From BBC News:
The creature was of the sauropod type – that group of long-necked, four-footed herbivores that were the largest of all the dinosaurs.
But at just a few metres in length, this animal was considerably smaller than its huge cousins, scientists report in the journal Nature. The team thinks the Jurassic species evolved its small form in response to limited food resources on an island. Martin Sander, from the University of Bonn, and colleagues studied the remains of over 11 sauropods found in a quarry at Oker, near Goslar, Lower Saxony. With total body lengths ranging from 1.7 to 6.2m (5.5-20ft), the team originally thought the dinosaurs were juveniles. But when the scientists examined the fossils closely, they realised they were dealing with dwarf creatures.
More here.